In waste incineration plants, refractory tiles are applied in order to protect the tube sheets from corrosive gases and temperature. These refractory tiles are suspended from stainless steel anchors which are welded onto the tube sheet. The refractory tiles are made of refractory material with a high content of silicon carbide (SiC). Generally the SiC-content is 85% or higher. On the one hand, SiC has a high heat transfer rate, allowing a maximum amount of energy to flow to the tube sheets. Furthermore, due to the high heat transfer, the hot side of the SiC tile remains relatively cool, such that slag remains from the incinerated waste do not stick easily to the tiles.
Because SiC is sensitive to oxidation above 900° C., the tiles may be pre-fired in the absence of oxygen and a nitride bond is created. Such tiles are therefore known as nitride-bonded silicon carbide (nSiC) tiles. However, after some time in use, generally after about 3 to 5 years, nSiC-tiles will also become sensitive to oxidation, and at a certain moment they will start to oxidise. One effect of this is a change in volume of approximately 5% on the hot side, which causes damage to the tile.
EP 2 383 532 A2 discloses refractory systems for lining interior walls of furnaces, comprising a porous refractory main body with a non-porous refractory layer. The main body and the non-porous layer may be separate plates connected together using a SiC-mortar. While this system may provide adequate corrosion protection within and below separate refractory elements, protection is lacking between separate elements, where corrosive gases, slag, oxygen, ash, debris or other objects may penetrate the refractory layer and damage the tube sheets below.